The present invention relates to a device for electrically controlling the idling of internal combustion engines, particularly in automotive vehicles having a comparator in which an idling speed-of-rotation/control deviation signal is formed which, with a speed-of-rotation regulator, controls a setting current which can be fed into an idle airflow setting member, and having means for adjusting the setting current.
In such devices assurance must be had that a minimum flow of air is fed in all cases to the internal combustion engine so that satisfactory stability of regulation and thus a dependable interception is obtained in the case of so-called sudden "zero" gas. The minimum airflow depends on the specific type of internal combustion engine to be regulated and on variables which change with time, such as dirtying of the throttle-valve region and of the setting member in a by-pass to the throttle valve, and a change in the frictional resistance of the engine. Furthermore, for example, changes in air temperature and air pressure affect the minimum airflow required. If the minimum airflow is not reached even in the most unfavorable case then there is the danger that in the case of sudden "zero" gas, i.e. upon sudden release of the gas pedal, the internal combustion engine will stall as a result of its inertia and the speed-of-rotation of the internal combustion engine will drop below a lower limit value.
Up to now, the minimum airflow has been adjusted as a function of the type of engine by a so-called first adjustment point of a setting member in the by-pass to the throttle valve. This was done, for instance, by adjustment via an adjustment screw on the setting member. This process required a large amount of time. Another possible way of preestablishing the minimum airflow consisted of adjusting the setting members prior to installation by statistical determination of the required minimum airflows for a given type of engine. This adjustment, however, increased the cost of manufacture of the device for the electric control of the idling. Aside from this, in both methods of adjustment a future change in the required minimum airflow could, in principle, not be taken into account.
In the last-mentioned method of adjustment, the minimum airflow was adjusted in particular by an electric setting member on the speed-of-rotation regulator, or a voltage-current transformer arranged behind it. In this way, the setting current feeding a setting member could not exceed the preset value. In this case one starts, for instance, from the basis that the maximum value and/or minimum value of the setting current sets the minimum flow of air with the setting member.
It is an object of the invention to develop a device for electric regulation of the idling speed of the aforementioned type in such a manner that the necessary minimum airflow is assured without time-consuming and costly adjustment processes upon the manufacture of the device for the idling regulation and/or of the vehicle even in the event of a subsequent change in the operating conditions of the internal combustion engine.